Because smooth running leads to less stresses, fatigue
and noise, most machines and structures are required to operate with low
levels of vibration. The information on this page provides
a brief overview of the principles and methods used to analyze the vibration
of rotating or reciprocating industrial machinery.

What causes vibration in industrial machinery?

out-of-balance rotating components

motor shaft not magnetically centered

cavitation/recirculation (as in pumps)

loose and/or worn chains and sprockets

loose or worn bearings

worn gears (inside gearbox)

loose anchoring bolts on gearboxes, motor mounts or idlers

application demands greater than machine's rated specification

alignment drift of components (e.g. couplings; chain/sprocket)

resonance (materials and components may have natural resonant frequencies)

What can lead to vibration in industrial machinery?

insufficient lubrication

improper alignment of components during set up (e.g. couplings; belts,
pulleys; chain/sprocket)

ambient environmental temperature

component-level manufacturer or material defect

application demands greater than machine's rated specification

Noise vs. vibration: can a vibration always be heard?

Many industrial environments are noisy so a problem may exist long
before it's "heard". Sometimes, the failing component never
be will be loud enough before failure. A low frequency vibration
(below 100Hz) may also not be audibly detectable.

Noise vs. heat.

A tell-tale clue that a component or machine is experiencing abnormal
mechanical stress is heat. Example: a noisy gearbox that is hot to touch.

Vibration
Monitoring:

The purpose of vibration monitoring is to ascertain the normal operation
of equipment or machinery in a manner that is objective and scientific.
While "expert" opinions regarding how a machine is running are useful,
they cannot substitute for scientific "metering" and analysis
to obtain the actual condition of rotating or reciprocating machinery.
In addition, there is no better criteria
for
operational reliability in rotating machinery than its vibrational characteristics.

Companies that use vibration monitoring and vibration analysis enjoy the
following benefits:

Less Downtime

Less Spare Parts Inventory

Improved Management Time Allocation

Less Maintenance

Longer Production Runs

Improved Product Quality

Recording vibration data can be done with tools as basic as a meter, pencil
and paper. Modern technology, however, offers a far better option: computer-assisted
data collection, which can provide far greater (and more
accurate) detail in a fraction of the time. There are many suppliers that
carry such instruments; alternatively, your company you may choose
to out-source a vibration-analysis team.

Predictive and preventive maintenance programs that employ this technology
allow for a promising new
source
of
profit
potential.
Greater profit can indeed be attained with a minimum of capital expenditure,
no layoffs and greater acquired skills.

Vibration Analysis

Using a vibration analyzer, trained personnel can pinpoint
the causes of rough machinery condition. Such problems as rotor imbalance
and
misalignment make up a great proportion of mechanical deficiencies and
can be identified and rectified. Other problems such as bearing wear are
not only detected, but also "rated" as to the severity of wear.
In many cases, an historical case study can prognose the remaining life
of bearings
so that repair schedules can be prioritized.

A predominant use of vibration analysis-based correction
is that of balancing. Balancing with an analyzer is a methodical, stepped
process -- it's more than a trial and error method of achieving dynamic
trueness.It's one of very few techniques where machinery which is deemed "rough" can
be corrected in place, without disassembly and where, in almost
all cases, the results can meet virtually any level of precision. Diagnosis
and cure are achieved with the same instrument.

Vibration analyzers can be used for running alignment. For example, an
analyzer can be used throughout the alignment procedure to detect the source
of high
vibration
or to detect the effects of fastening. Also,
soft-foot conditions can be detected and corrected while the machine is
operational. This allows for a quick diagnosis and correction
without having to stop and start the equipment.

There are many other instances of vibration monitoring, analysis, balancing
and corrective measures that make this technology so effective.

False
Beliefs, Assumptions and Wishful Thinking

"We don't have a vibration problem"

"vibration" is not a "problem" per se. It's a physical manifestation
of machinery imperfection. It can be used as a tool to help find obvious
and subtle deviations in machines. No machine runs "perfect".

"Align or balance that machine"

This is a request that is made before a condition of imbalance is established.
It's not just a matter of semantics either. If the machine is imbalanced, corrective action can be taken and the machine can operate
within tolerances. If it's not imbalanced, the vibration analyst will
advise the corrective action but cannot use the analyzer to fix the problem
directly. It's a matter of expectations and in some cases, disillusionment.

"That machine is running fine -- we just changed the bearings"

This is often stated as a reason for not analyzing a machine.
Bearings do fail. After a certain amount of time, maybe a month, maybe
a years,
bearings
will finally succumb to slight or severe wear criteria
and will fail. Assuming that bearing replacement is the final
solution is a wishful thinking.

The bearing replacement trap occurs when the old bearings are noisy or
fail. The technicians replace them and the new ones
are now quiet. Problem solved, right? Wrong!

Bearing failure could be an indication of the natural expected life of
the bearing itself but it should send alarm bells that this is a primary
candidate for analysis. The failure could be the result of the mechanical
deviations in a machine that could be corrected if one were to know about
them. Also, the best time to get a vibration profile for future comparisons
is when the machine has been reconditioned. This helps to find any inherent
fault in the machine as well as determine if the work performed
on it was done to specification. Also, remember the best maintenance programs
are the ones that
have the most historical information.

"That machine always runs like that"

And it always will until you fix it! Vibration analysis can tell you how.

"When it breaks, we will fix it"

The fact is, the machine will fail at its discretion and
not to your schedule. When it fails, it will cause secondary damage. The
parts for many machines must be kept on hand ahead of time to minimize
the time it takes to repair. Plant production will cease. Personnel will
be reallocated.

However, A more sensible approach leads to efficient,
cost-effective action:

"We replace worn parts before they fail"

Using vibration analysis, you have a list of "invisible" anomalies.
This list will show problems long before failure which will allow repairs
to be scheduled during off hours. Problems with bearings are detected long
before they fail so that other associated mechanical components are unaffected.
Parts are not seized, no shafts are broken so the repairs are done in a
fraction of the time. During repairs, other machines that have impending
problems detected with vibration monitoring can be corrected. The parts
have been ordered as needed. top of page | How to choose
a Vibration Analyzer

"The natural frequency of many single-degree-of-freedom systems
can be determined by evaluating the characteristics of the strain energy
and the kinetic energy of each system..."

From Book News, Inc.
Without noting the dates for the first two, Steinberg (U. of California-Los
Angeles) has made extensive changes in the third edition to reflect
the dramatic reduction in electronics that makes them affordable in
many applications that were once good enough as mechanical devices.
A major concern of his is the adoption of commercial equipment and
standards by the military. Among the new chapters are discussions of
the effects of manufacturing methods and tolerances on the reliability
of the electronic hardware, methods for improving the ruggedness of
commercial hardware for improved reliability in harsh military environments,
the bending distortion of the circuit board at its resonant condition,
and environmental stress screening.Book News, Inc.®, Portland,
OR

Book Description:
This book deals with the analysis of various types of vibration environments
that can lead to the failure of electronic systems or components.

Reviews:

Application beyond just electronics
The author is obviously an engineer who understands the everyday practical
problems a dynamicist faces. Some theory, but chock full of easy to
understand, and more importantly, *useful* information necessary to
put properly designed product out the door.

Don't let the title fool you. The focus of this book is electronics,
but the material here is applicable to any vibration problem.

If you're doing any dynamics work, you NEED this book.

A tool for success
If a mechanical engineer has chosen a career in the world of electronics,
I strongly recommend this easy to follow gold mine of a book. I say it's a gold mine because it applies directly to the engineers' job.
There are no fluff chapters or topics. Everything applies. Steinberg
has made it easy (and almost fun) to solve those every day shock, vibration
and acoustic challenges. Finding the natural frequency of a body such
as a PC board is so much simpler for me now. And a surprising tidbit
was for me to discover some amazing facts concerning acoustics. This
is especially important as applied to fan cooled electronic packages.
Another important area of study was packaging for transportation. How
many times have we simply said "Just pack it in foam"? Before
reading this book, I couldn't be sure what foam density to use or what
the optimum thickness was. Why guess? Do it right.

I borrowed this book from my employer, took it home and read it over
the long Christmas weekend. I was so impressed, that I am purchasing
my personal copy tonight. I won't be without it.

This Book is to the point, get it done, structural dynamics.
This reference is a must read for any structural engineer entering into
the the electronic packaging world. You can't go wrong with the easy
to understand examples and extra insight the book gives to the rapid
engineering production world we live in today.

From Book News, Inc.
Ninety percent of all machine failures are signaled months, even years,
in advance by changes in machine vibrations. Wowk shows how to use
state-of-the-art instrumentation--transducers and fast Fourier transform
(FFT) spectrum analyzers--to monitor machine conditions using the
vibration "signature" of the machine. Includes a diagnostic
chart for assessing the severity of vibration, and case histories
that illustrate strategies for solving machinery problems. Annotation
copyright Book News, Inc. Portland, Or.

Book Description:
Presents, in a single source, a practical, "hands-on" approach
to vibration analysis and measurement, field balancing and shaft alignment,
and how to understand and solve typical vibration problems. It covers
balancing, resonance, gears and bearings, structural vibration, isolation,
alignment, instruments, diagnostics, and trending. Includes extensive
coverage of the FFT spectrum analyzer as well as numerous ``fixes''
to help solve immediate vibration problems. Presents principles applicable
to all mechanical equipment as well as many case histories covering
various mechanical devices such as fans, common motors, and pumps

Reviews:

Overall Best Vibration Book Yet
As a practicing mechanical engineer and vibration analyst for over
eight years, I have found Mr.Wowk's book the best yet. In particular,
I have found this book to have a good index and sensibly ordered
so information can be obtained quickly. Also, Mr.Wowk has smartly
avoided extensive mathmatical discussions in his book and focused
the content towards common problems and solutions. To improve his
book I would recommend more case histories and more extensive content
on topics such as electrical problems and bearing faults. Overall it's the best book of its type I have read yet.

About the books description from the author's wife
This textbook is basically about the technology of machinery vibration
measurement and analysis. It touches on topics such as balancing
and alignment, but does not cover these subjects in detail. Victor
has written subsequent textbooks that cover balancing and alignment
in detail. The [above] description about this book is correct except
for the Synoposis which describes the textbook: Machinery Vibration:
Balancing. I know Victor's textbooks intimately--since I word processed
all three of them. Of course I highly recommend reading them. As
an office manager with no experience in plant maintenance, I gained
a basic understanding in the field of vibration analysis. I have
seen that when companies utilize this technology, production downtime
is minimized, and costs in maintaining rotating equipment and facilites
are dramatically reduced--a must read for company decision makers,
such as facility or plant managers, purchase agents, and executives.
Of course maintenance techs and engineers also can benefit from reading
this book. (Victor teaches private and public workshops based on
his books--visit www.machinedyn.com for details.)

Well written with a focus on the fundmentals
A great book for anyone interested in basic vibration analysis. Good
coverage of vibration theory and application. Included are case histories
that help demonstrate how to apply vibration techniques. If you want
a better understanding of machinery vibration with a focus on real
world application this is a best buy.

From Book News, Inc.
A 127-page handout for alignment courses at the Los Alamos National Laboratory
designed to provide practical knowledge to the hands-on person who
must perform the task has here developed into a broad overview of the
alignment process that contains all the common methods and tools, including
a chapter on lasers. Wowk points out that misalignment is a major source
of vibration in machines with components that have relative motion.
Two earlier volumes on machinery vibration cover measuring and analysis,
and balancing; a fourth, on resonance and isolation, will complete
the series.Book News, Inc., Portland, OR

One of the most common causes of severe machinery vibration is the misalignment
of drive shafts and other components. Machinery Vibration: Alignment,
by Victor Wowk, gives you a practical resource for aligning shafts, bearings,
gears, pulleys and a wide variety of power transmission components in
machines without further training. You get step-by-step procedures for
balancing, resonance, structural vibrations, isolation, instruments,
diagnostics, and trending. Many of the methods described require only
simple tools, eliminating the need for a $20,000 laser alignment system.

Case studies covering everything from simple fans to high-speed turbines
give you examples of real-world problem solving. You will find the extensive
coverage of the FFT spectrum analyzer a valuable addition to this hands-on
toolkit.